IV. 



THE ANTHOCEROTHS I39 



or less united, and form a sort of network in whose interstices 

 the spores He. 



The development of the spores can Ije easily lollow^ed, at 

 least in most of the details, in fresh material, and on this 

 account it was among the first plants in which cell division was 

 studied. The mother cells in all stages can be found in the 

 same sporogonium, and on account of their great transparency 

 show the process of cell division very satisfactorily. The 

 nucleus, however, is small, and its behaviour during the cell 

 division is not so easy to follows The mother cell, just before 

 division, is filled with colourless cell sap, and the cytoplasm is 

 confined to a thin film lining the cell w^all. This cytoplasmic 

 layer is somewhat thicker on one side, and here the nucleus is 

 situated (Fig. y^^, A). Lying close to the nucleus is a round- 

 ish body, of granular consistence and yellowish green in colour. 

 This is a chloroplast, which at this stage is less deeply col- 

 oured than later. The chloroplast contains a number of 

 granules, some of w^hich are starch. The cell increases rapidly 

 in size, and the nucleus, together wath the chloroplast, move 

 aw-ay from the wall of the cell toward the centre, where they 

 are suspended by cytoplasmic threads. The chloroplast next 

 divides into two equal portions, which move apart (Fig. 73, 

 B), but remain connected by the cytoplasmic filaments. They 

 approach again, and each dividing once more, the four result- 

 ing chloroplasts remain close together with the nucleus, in the 

 centre of the cell. 



Davis ( I ) has made a very complete study of the spore 

 division in A. Iccvis. In this species the archesporium is less 

 massive than in A. Pearsoni or A. fiisiforuiis, and the ar- 

 rangement of the sporogenous and sterile cells less regular. 

 Davis found that the sporophytic nuclei had regularly eight 

 chromosomes, those of the gametophyte four. 



Owing to the small amount of chromatin in the nucleus, 

 the karyokinetic figures are small and the changes difficult to 

 follow satisfactorily. Enough can be easily made out, how-* 

 ever, to show that the process is in no w^ay peculiar. There is 

 first a nuclear spindle of the ordinary form, and the resulting 

 nuclei assume the resting stage before dividing again. Each 

 then divides, and the four nuclei move to points equi- 

 distant from each other, and which are already occupied by the 

 four chloroplasts. After this is accomplished, cell walls arise 



